It is the long-range goal of this project to study the co-oxygenation of xenobiotics by prostaglandin synthetase, particularly the pulmonary prostaglandin synthetase. The generation of toxic intermediates, carcinogens, mutagens, etc., during the co-oxygenation will be investigated. Topics of current interest are the co-oxygenation of benzopyrene during the metabolism or arachidonic acid by guinea pig lung, ram seminal vesicle microsomes, and cells grown in tissue culture. BP was oxidized to quinones by PG synthetase. Electrophilic metabolites of BP were formed since BP was found covalently linked to protein and DNA. Significance of this metabolic activation in relation to cell transformation is being examined.